This invention relates to an apparatus for opening an elongated bag containing an article by slitting the wall of the bag.
One well known apparatus for slitting the wall of an elongated bag is schematically illustrated in FIGS. 1 and 2. This apparatus includes a support member 9 defining a V-shaped, horizontally extensive groove 11 (FIG. 2). A cutter assembly is provided, such cutter assembly including a large number of blades 1a through 1n fixed to a pair of blade support plates 2 and 3 by bolts 4a through 4n. The cutter assembly is disposed above the support member, and the blades 1a through 1n being disposed in a row extending parallel to the axis of groove 11. As shown in FIG. 1, the cutter assembly is movably mounted to the frame of the apparatus. A link 6 is rotatably connected at one end of a fixing plate 5 by a bolt 7, fixing plate 5 in turn being fixedly connected to the frame of the apparatus (not shown). The other end of link 6 is rotatably connected to the cutter assembly by a bolt 8 at one end of the cutter assembly. A similar arrangement of link 6a, fixing plate 5a and bolts 7a and 8a is provided at the opposite end of the cutter assembly. A plurality of vertically movable grippers 10, of which only one is illustrated in FIG. 2, are provided. These grippers are disposed above the support member 9 and above the cutter assembly. The grippers are arranged in a row extending along the length of groove 11.
In operation, an elongated bag A, containing an elongated article is disposed on support member 9 so that the bag rests in the groove 11 substantially coaxially therewith. The support member is then elevated to the position indicated in broken lines in FIG. 2 so that the bag is adjacent the grippers 10. The grippers 10 are then actuated to engage the bag wall and are moved upwardly to pull the engaged portions of the bag wall upwardly away from the article enclosed in the bag and thus form a crease extending upwardly from the remainder of the bag along the entire length of the bag. The cutter assembly is then moved from the retracted position illustrated in solid lines in FIG. 1 to the extended position partially illustrated in broken lines in FIG. 1. During such movement, each of the links 6 and 6a swings about the associated one of the bolts 7 and 7a so that the cutter assembly moves in an arcuate fashion towards the medial plane of groove 11. During such motion, each of the blades 1a through 1n punctures the wall of the bag above the article contained in the bag and each of the blades forms a short longitudinal cut in the bag wall. If the blades 1a through 1n are precisely coplanar with one another, the cuts formed by the various blades merge into a single continuous slit extending along the entire length of the bag.
In practice, however, it is difficult to maintain all of the blades in such coplanar relationship with one another. Therefore, there will be discontinuities in the slit at the junctures between the cuts made by adjacent blades. When the bag is pulled open and the article removed therefrom in a subsequent processing operation, small pieces of the bag wall may be torn from the bag at such discontinuities and deposited on the article or on the equipment utilized for removing the article. For example, if the article contained in the bag is a stack of can lids for use in food canning operations any pieces of the bag wall which become detached from the bag in this manner may contaminate the lids.
Moreover, a large number of blades and a large number of grippers must be provided if the bags to be opened are of substantial length. Such multiple components are undesirable, as they increase the cost of the apparatus and make it more difficult to maintain.